Microbiological Quality and Antimicrobial Resistance Risks in Marketed Dairy Products: A Comparative Study of Contamination and Probiotic Safety in India

Abstract

Dairy products are essential sources of nutrition but they are highly vulnerable to microbial contamination and the emergence of antimicrobial resistance (AMR). The present study combines two supplementary studies: (i) micro biology quality evaluation of dairy products of various markets in India and (ii) the occurrence of antibiotic resistance in Lactobacillus strains on packed commercial curd. Fifty market dairy samples (milk, paneer, tofu, yogurt, butter, and cheese) were screened by the standard methods Total Plate Count (TPC), coliform enumeration, and pathogen (Escherichia coli, Salmonella spp., Staphylococcus aureus, and Listeria monocytogenes) detection. In parallel, adulteration testing, microbial enumeration, and antibiotic sensitivity profiling of Lactobacillus isolates with the disc diffusion method were performed on branded curd samples of Amul, Nestle, and Mother Dairy. Findings showed a prevalence of microbial levels above acceptable market sample levels (~ 40 percent) in unpasteurized milk and soft cheese. In 20 percent of samples, pathogenic bacteria were found, which highlights the risks associated with poor hygiene and handling. Compared to packed dairy products, packed dairy products registered lower loads of microbes, but surprisingly, multidrug-resistant Lactobacillus strains were found in them. All the tested were resistant to Polymyxin B (100%), and some were also resistant to Penicillin G (43.7%), suggesting the risks of horizontal gene transfer in the human gut. Combined, these results point to a two-fold public health problem: contamination of pathogens in uncontrolled dairy markets and the silent spread of AMR in branded dairy with probiotics. The research indicates that combined microbiological surveillance, increased enforcement of hygiene standards and resistance profiling of probiotic strains are required in the Indian dairy sector